Engine starter drive



E. E. HOOD ENGINE STARTER DRIVE Filed June 27, 1942 Oct. 12, 1943.

' INVENTOR. Y B? a WW TORNEY Patented Oct. 12, 1943 E. Elliott Hood, Elmira, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application June 27, 1942, Serial No. 443,708

Claims.

The present invention relates to engine starter drives and more particularly to a device for preventing undesired engagement of a starter drive pinion with the gear of an engine to be started.

In engine starter gearing of the type in which a pinion is automatically moved into and out of engagement with an engine gear by virtue of a threaded driving connection, there is a tendency for the pinion to bound back into engagement with the engine gear when it is thrown out as the engine starts. There is also a tendency for the pinion to drift into engagement with the engine gear while the engine is running, due to vibration, particularly at certain engine speeds.

Since this undesired engagement of the pinion With the engine gear causes a gradual attrition of the parts, various means have been devised to overcome these tendencies. It has been generally customary, however, to utilize separate devices for rebound checks and for antidrifts, and the resultant structure has sometimes been unnecessarily complicated and expensive.

It is an object of the present invention to provide a novel combined rebound check and antidrift means for a starter drive which is efiicient and reliable in operation and simple and economical in construction.

It is another object to provide such a device which is readily adapted to existing forms of drive with very little added operation or complication.

It is a further object to provide such a device in which the activating element is readily replaceable without dis-assembly of the drive.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of a starter drive embodying a preferred form of the invention;

Fig. 2 is a similar view showing the parts in driving position;

Fig. 3 is a section taken substantially on the line 3-3 of Fig. 1; and

Fig. 4 is a view similar to Fig. 1 showing the rebound check in action.

In Fig. 1 of the drawing there is illustrated a power shaft 1 which may be the extended armature shaft of the starting motor not illustrated. A pinion 2 is slidably journalled on the power shaft for movement into and out of engagement with a member such as a gear 3 of an engine to be started. Means for actuating the pinion from the power shaft is provided comprising a hollow sleeve 4 having an enlarged drivinghead 5 fixed to the power shaft l as by means of a pin 6; A stop nut l. is fixed on. the end of the sleeve 4 and a screw shaft 8 is slidably journalled on said sleeve, between the stop nut and a thrust washer 9, bearing against a shoulder ll formed by the driving head 5.; Screw shaft 8-is rotated from the driving head 5 through a spring l2 anchored to the driving head by a driving anchor member l3 fixed thereon, and to the screw'shaft by a driven anchor member l4 non-rotatably mounted on a driven head [5 on the screw shaft.

A nut I6 is threaded on the screw shaft and rigidly connected to the pinion 2 by means of a barrel member H. The idle position of the nut I6 is defined by a shoulder l8 on the screw shaft, and the travel of the nut toward operative position is limited by engagement thereof with the stop nut l on the sleeve 4.

According to the present invention unitary means are provided for frictionall maintaining the nut H5 in idle position on the screw shaft 8, and also for preventing rebounding of the nut and its associated parts toward operative position when the pinion is thrown out of engagement with the engine gear as the engine starts. As here shown, this means is in the form of a flat spring member I9 mounted in a recess 20 (Fig. 3) in the interior of the nut l6, and bowed inwardly so as to bear frictionally on the threads of the screw shaft. The spring 19 is anchored to the nut so as to travel longitudinally therewith by means of a hook 2| formed on the inner end of the spring which is arranged to enter an opening 22 in the nut. In order to increase the effectiveness of the spring l9 as an anti-drift, the threads of the screw shaft 8 may be turned down adjacent the idle position of the nut so as to form an inclined shoulder 23 (Fig. 2) over which it is necessary for the spring to be forced in order to move the pinion into operative position.

The outer end 24 of the spring I 9 is arranged to extend beyond the nut l6 so as to engage the shoulder I8 of the screw shaft before the nut it reaches the end of its travel. Such engagement causes the spring l9 to be forcibly pressed inward against the screw shaft to increase its frictional engagement thereon and thus dissipate the energy of the pinion and barrel assembly when it is thrown out of mesh.

In operation, the rotation of the power shaft I by the starting motor in the direction of the arrow causes the nut I6, barrel l1 and pinion 2 to move to the right to cause engagement of the pinion 2 with the engine gear 3, this engaging movement being limited by abutment of the nut I 6 against the stop nut 1. The pinion is then constrained to rotate with the power shaft, causing the engine to be cranked. When the engine starts, the acceleration of the pinion causes it to be de-meshed and the pinion and barrel assembly thrown back to idle position. As the nut 16 approaches the shoulder 18 on the screw shaft, the end 24 of the spring IQ engages said shoulder, causing the spring to be forcibly pressed against the screw shaft to frictionally arrest the relative rotation between the nut and screw shaft.

Thereafter the pinion assembly is maintaineq idle position by the normal frictional engagement of the sprin I 9 on the screw threads, shop-l der 23 on the screw shaft serving to prevent drifting of the pinion assembly due to vibration of the engine or other causes.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that various aha gesmay be made intlie' design "and 'ar'rangemn tof the parts without departing mi i theispilri tof'the invention as canned the-c1aims appended hereto;

"What is clain'iedis:

1. In an engine starter drive a screw shaft, a nut threaded thereon for rnovementinto and out of operative position, a flat spring member mounted in the interior of the nut bearing frictionally on the screw shaft, andrn'eans' engaging the end of the spring to arrest the movement of the nut away from operative position.

2. An engine starter drive as set forth in claim 1 in which the engagement of the spring with the arresting means causes the spring to be flexed to increase its pressure on the screw shaft.

3. A starter drive as set forth in claim 1 in which the spring is bowed axially of the drive with its middle portion bearing on the screw shaft and the inner end of th spring is connected for longitudinal movement with the nut.

, '4. A starter drive as set forth in claim 1 in the spring is bowed axially of the drive with'its middle portion bearing on the screw shaft; said nut having an opening, and the inner end of the spring being bent into the opening to connect the spring for longitudinal movement with t li- 5. In an engine starter drive a screw shaft, a pinion, a nut rigidly connected to the pinion and threaded on the screw shaft to move the pinion missile out of engagementwith'arnembefof an engine to' be started, 'a" spring'membe'r attached tothe nii't bearing frictionally on the screw sin-n, said screw shaft having a shoulder adjacent the idle position of the s ring, and an "abutment adapted to engage the spring to'lim'it movement of the nut away'from operative position, said engage'mnt being arranged to increase the frictiona1 bearing of the spring'on the screw shaft.'

' E. ELLIOT'I Hoop. 

